System for forming composite polymer dielectric film

ABSTRACT

A system for depositing a composite polymer dielectric film on a substrate is disclosed, wherein the composite polymer dielectric film includes a low dielectric constant polymer layer disposed between a first silane-containing layer and a second silane-containing layer. The system includes a process module having a processing chamber and a monomer delivery system configured to admit a gas-phase monomer into the processing chamber for deposition of the low dielectric constant polymer layer, a post-treatment module for annealing the composite polymer dielectric film, and a silane delivery system configured to admit a vapor flow containing a silane precursor into at least one of the process module and the post-treatment module for the formation of the first silane-containing layer and the silane-containing layer.

BACKGROUND

Integrated circuits contain many different layers of materials,including dielectric layers that insulate adjacent conducting layersfrom one another. With each decrease in the size of integrated circuits,the individual conducting layers within the integrated circuits growcloser to adjacent conducting layers. This necessitates the use ofdielectric layers made of materials with low dielectric constants toprevent problems with capacitance, cross talk, etc. between adjacentconducting layers.

Low dielectric constant polymers have shown promise for use asdielectric materials in integrated circuits. Examples of low dielectricconstant polymers include, but are not limited to, fluoropolymers suchas TEFLON ((—CF₂—CF₂—)_(n); k_(d)=1.9) and PPX—F((—CF₂—C₆H₄—CF₂—)_(n);k_(d)=2.23). Many of these materials have been found to be dimensionallyand chemically stable under temperatures and processing conditions usedin later fabrication steps, have low moisture absorptioncharacteristics, and also have other favorable physical properties.

However, many low dielectric constant polymers have been found to adherepoorly to silicon-containing layers that are commonly used in integratedcircuits, including but not limited to silicon oxide, silicon nitride,silicon carbide, and SiO_(x)C_(y)H_(z). Furthermore, the syntheses usedto create these films may leave many unreacted free radical chain ends,which may be susceptible to contamination by water, oxygen, and othermaterials that may reduce the dimensional and chemical stability of thefilm under increased temperatures. These problems may result inunreliable device fabrication and low device yields.

SUMMARY

One embodiment provides a system for depositing a composite polymerdielectric film on a substrate, the composite polymer dielectric filmincluding a low dielectric constant polymer layer disposed between afirst silane-containing layer and a second silane-containing layer. Thesystem includes a process module having a processing chamber and amonomer delivery system configured to deliver a gas-phase monomer to theprocessing chamber for deposition of the low dielectric constant polymerlayer, a post-treatment module for annealing the composite polymerdielectric film, and a silane delivery system configured to deliver avapor flow containing a silane precursor into the system for theformation of the first silane-containing layer and the secondsilane-containing layer. The system also includes memory and a processorin electrical communication with the process module, the post-treatmentmodule and the silane delivery system, wherein the memory includesinstructions stored thereon executable by the processor to deposit thesilane precursor on the substrate for a first interval to form the firstsilane-containing layer, deposit the gas phase monomer on the firstsilane-containing layer for a second interval to form the low dielectricconstant polymer layer, and deposit the silane precursor on the lowdielectric constant polymer layer for a third interval to form thesecond silane-containing layer.

Another embodiment provides a system for depositing a composite polymerdielectric film on a substrate, the composite polymer dielectric filmincluding a low dielectric constant polymer layer disposed between afirst adhesion promoter layer and an overlayer, wherein the overlayerincludes at least one layer selected from the group consisting of asecond adhesion promoter layer, an etch stop layer and a hard masklayer, and wherein the first adhesion promoter layer includes reactivesilane groups configured to chemically bond to a silicon-containinglayer that is in contact with the adhesion promoter layer. The systemincludes a process module for forming the low dielectric constantpolymer layer, wherein the process module includes a deposition chamber,a substrate holder configured to hold and cool a substrate during adeposition process, and a monomer delivery system for delivering agas-phase diradical monomer to the deposition chamber; a post-treatmentmodule for annealing the composite polymer dielectric film, wherein thepost-treatment module includes a heat source for heating the substrateand a processing gas delivery system for delivering a reducing gas tothe post-treatment module; a silane deposition module for depositing thefirst adhesion promoter layer and the overlayer, wherein the silanedeposition module includes a silane deposition chamber and a silanedelivery system for delivering silane precursor to the silane depositionchamber; and a transfer module operatively connected to the processmodule, the silane deposition module and the post-treatment module,wherein the transfer module includes a substrate transport mechanism fortransferring a substrate among the process module, the silane depositionmodule and the post-treatment module.

Another embodiment provides a computer-readable storage mediumcontaining instructions stored thereon, wherein the instructions areexecutable by a processor on a wafer processing system to direct thewafer processing system to perform a method of forming a compositedielectric film on a wafer, the composite dielectric film including anadhesion promoter layer having a plurality of silane groups, and a lowdielectric constant polymer layer disposed on the adhesion promoterlayer and chemically bonded to the adhesion promoter layer. The methodincludes depositing a silane material onto the wafer, exposing thesilane material to a free-radical generating energy source to generatefree-radicals from vinyl, keto or alkyl halide functional groups on thesilane material and to form the first adhesion promoter layer,depositing the low dielectric constant polymer layer on the adhesionpromoter layer by exposing the wafer to a concentration of a gas phasefree radical, and heating the first adhesion promoter layer and the lowdielectric constant polymer layer in the presence of hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a greatly magnified sectional view of an embodiment of acomposite polymer dielectric film, formed on an underlying substrate.

FIGS. 2 a-2 f show chemical reactions that may occur between theunderlying substrate and adhesion promoter layer, within the adhesionpromoter layer, and between the adhesion promoter layer and polymerdielectric layer of the embodiment of FIG. 1.

FIG. 3 is a flow diagram showing an embodiment of a method of forming acomposite polymer dielectric layer on a substrate.

FIG. 4 is a flow diagram showing another embodiment of a method offorming a polymer dielectric layer on a substrate.

FIG. 5 is a block diagram of an exemplary embodiment of a system forforming a composite dielectric layer on a substrate.

FIG. 6 is a block diagram of another exemplary embodiment of a systemfor forming a composite dielectric layer on a substrate.

FIG. 7 is a plan view of an exemplary embodiment of a system for forminga composite dielectric layer on a substrate.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS

FIG. 1 shows, generally at 10, a first exemplary embodiment of acomposite polymer dielectric film formed on a substrate 12. Compositepolymer dielectric film 10 includes a first silane-containing adhesionpromoter layer 14 disposed on substrate 12, a low dielectric constantpolymer layer 16 disposed on first adhesion promoter layer 14, and asecond silane-containing layer 18 disposed on low dielectric constantpolymer layer 16. Composite polymer dielectric film 10 is typically usedas an interlayer in an integrated circuit. Thus, other layers (not shownfor purposes of clarity) are typically formed over secondsilane-containing layer 18. While layer 18 is described in some of thedepicted embodiments as being a second adhesion promoter layer, it willbe appreciated that layer 18 also may be a hard mask layer or an etchstop layer, such as those used in single and dual damascene processes.Each of these variations is described in more detail below.

As described above, low dielectric constant polymer layer 16 may beformed from materials such as TEFLON, PPX—F and other similar materials.While possessing a low dielectric constant, these materials may notadhere to underlying layers with enough force to withstand the rigors ofdownstream processing steps. For example, when deposited directly on alayer of silicon oxide or silicon carbide (which are commonly used inintegrated circuits), PPX—F adheres to the layer with a yield strengthof approximately 2-3 MPa, indicating that the adhesion of the PPX—F filmto the silicon oxide or carbide layer is primarily due to Van der Waalsinteractions. PPX—F may adhere to other silicon-containing layers withsimilar yield strengths. In contrast, a film should adhere to anunderlying or overlying layer with a yield strength of approximately 4-5MPa for the structure to safely withstand subsequent back-end processingsteps. The use of a properly selected adhesion promoter layer 14 mayhelp to increase the yield strength of the low dielectric constantpolymer layer 16 on an underlying or overlying silicon-containing layersufficiently to equal or surpass a desired yield strength thresholdwithout raising the dielectric constant of the overall composite polymerdielectric film 10 an undesirable amount.

First adhesion promoter layer 14 is formed from a material capable offorming chemical bonds to both substrate 12 and low dielectric constantpolymer layer 16. One example of a suitable class of materials to use toform first adhesion promoter layer 14 are silanes having a generalstructure of(RZ)_(x)-Si—(W-T)_(y)   (I)wherein W is selected from the group consisting of —O—, —CH₂—,—(CH₂)_(a)C═OO—, and —(CH₂)_(a)—OO═C—; wherein T is selected from thegroup consisting of —CR═CR′R″, an alkyl halide, and —RC═O; wherein Z isselected from the group consisting of O and NR, wherein R, R′ and R″ arean H, alkyl or aromatic group; wherein a is 0 or an integer; whereinx=1, 2 or 3; wherein y=1, 2 or 3; and wherein x+y=4. Alternatively, RZcan be H. Such materials are capable of forming strong Si-Z-Si chemicalbonds (Z=O or NR, wherein R is an alkyl or aromatic group) to anunderlying silicon-containing substrate.

A more specific example of compounds of the general formula (I) includevinyl compounds having the general formula(RZ)_(x)-Si—(W—CH═CH₂)_(y),   (II)wherein W may be selected from —O— (such as a vinyl ether) —CH₂—,—(CH₂)_(a)COO— (such as a vinylacetyl-) and —(CH₂)_(a)OOC— (such as avinylactylo-), wherein Z is selected from the group consisting of O andNR, wherein R is an alkyl or aromatic group, wherein a is zero or aninteger, wherein x=1, 2 or 3, wherein y=1, 2 or 3, and wherein x+y=4.The vinyl group of these compounds is able to undergo a free radicalpolymerization with vinyl groups on adjacent vinyl silane molecules,thus helping to form a robust, polymerized adhesion layer that ischemically bonded to the adjacent silicon-containing layer. Where y=1 instructure (II) above, a linear vinyl polymer with side silane groupsbonded to the underlying silicon layer is produced. Where y=2 or 3, across-linked vinyl polymer is produced.

Another specific example of a suitable class of materials of generalformula (I) for forming adhesion promoter layer 14 are keto-containingsilanes (“Keto silanes”) having a general structure of(RZ)_(X)-Si—(W—RC═O)_(y),   (III)wherein R is an alky group, wherein W is CH₂ or (CH₂)_(a), and wherein ais an integer from 1 to 5.

Yet another example of a suitable class of materials of general formula(I) to use to form adhesion promoter layer 14 are halide-containingsilanes (“Halide-silanes”) having a general structure of(RZ)_(x)-Si—(W—X)_(y),   (IV)wherein X is a halide, typically Cl, Br or I.

All the above-mentioned vinyl, keto and halide silanes can undergo freeradical polymerization when initiated by a suitable energy source, suchas UV radiation. For example, under UV irradiation, the followingreactions can happen:(CH₃)₃—O—Si—CH₂—Cl→(CH₃)₃—O—Si—H₂C*+*Cl   (A)(CH₃)₃—O—Si CH₂—C═O(CH₃)→(CH₃)₃—O—Si—H₂C*+*C═O(CH₃)   (B)and(CH₃)₃—O—Si—CH₂—O—C═O(CH═CH₂)→(CH₃)₃—O—Si—CH₂—O—C═O(*CH—*CH₂)   (C)

Furthermore, some free radicals in first adhesion promoter layer 14 maynot react with other silane molecules, and instead may undergo a freeradical reaction with low dielectric constant polymer layer 16.Synthesis of low dielectric constant polymer layer 16 (described in moredetail below) may be carried out by transport polymerization of a gasphase diradical monomer species that is able to polymerize uponcondensing on a substrate surface from the gas phase. During transportpolymerization, some diradical monomers may react with unreacted vinylsilane-, keto silane- or halide silane-derived free radicals in firstadhesion promotion layer 14, thus chemically bonding first adhesionpromoter layer 14 with low dielectric constant polymer layer 16. Thus,by chemically bonding to both substrate 12 and low dielectric constantpolymer layer 16, adhesion promoter layer 14 greatly improves theadhesion of the low dielectric constant polymer layer to the substrate.

FIGS. 2 a-2 f illustrate an exemplary series of chemical reactionsbetween the acrylosilane (C₂H₅O)₃Si(CH₂)_(x)OOC—CH═CH₂, an underlyingsilicon-containing substrate, and an overlying low dielectric constantlayer of PPX—F formed from the deposition of the *CF₂C₆H₄CF₂* diradicalmonomer. First referring to FIG. 2 a, the silane functional group of thesilane molecule may react with surface oxygen typically found on thesurface of a silicon-containing substrate via an elimination of anOCH₂CH₃ leaving group. Here, the surface oxygen in thesilicon-containing substrate is shown as being bonded to a hydrogenatom. This bond may be a hydrogen bond, and the hydrogen atom may bepart of a water molecule, or the OH may be a hydroxyl group bonded tosubstrate 12. In either case, the reaction of the silane group with thesurface oxygen results in the formation of a chemical bond between thesurface oxygen and silicon atom of the silane group, and the productionof ethanol from the ethoxide leaving group. In the depicted embodiment,the formation of a single Si—O—Si bond is shown. However, it will beappreciated that more than one Si—O—Si (or, more generally, a Si-Z-Si)bond may form, potentially up to the number of (RZ) leaving groups onthe silicon atom in the silane.

Once the silane has been deposited on substrate 12, the silane layer maybe exposed to a suitable energy source, including but not limited toheat, UV light or a plasma, to generate free radicals on the silanemolecules. This permits the silane molecules to polymerize to formadhesion promoter layer 14, as depicted in FIG. 2 b. Furthermore, asdepicted in FIG. 2 c, some free radicals in adhesion promoter layer 14may react with free radicals in low dielectric constant polymer layer 16during deposition of the low dielectric constant polymer layer, thuschemically bonding first adhesion promoter layer 14 to low dielectricconstant polymer layer 16, as shown in FIG. 2 d.

After completing the deposition of low dielectric constant polymer layer16, second adhesion promoter layer 18 may be deposited onto the lowdielectric constant polymer layer and exposed to a suitable energysource to generate free radicals from silane molecules in the secondadhesion promoter layer (not shown in FIGS. 2 a-2 f) in the same manneras shown for first adhesion promoter layer 14. This permits the silanemolecules in the second adhesion promoter layer to polymerize, thusforming a strong polymer layer. Furthermore, this permits some radicalsin second adhesion promoter layer 18 to react with unreacted freeradicals in low dielectric constant polymer layer 16 to bond the secondadhesion promoter layer to the low dielectric constant polymer layerwith strong covalent bonds. The result is that the layers of compositedielectric film 10 are chemically bonded together, and that the surfacesof the composite dielectric film include many pending silane groupscapable of forming strong chemical bonds to adjacent silicon-containing(or other) layers.

In some embodiments, composite polymer dielectric film 10 may beannealed after formation examples of suitable annealing processes aredescribed in more detail below. Annealing composite polymer dielectricfilm 10 may help to improve the crystallinity and phase stability of thelow dielectric constant polymer layer, as described in U.S. Publishedpatent application Ser. No. US2003/0036617 to Chung Lee, filed Aug. 9,2001, the disclosure of which is hereby incorporated by reference.Furthermore, composite polymer dielectric film 10 may be annealed in thepresence of hydrogen gas to cap any unreacted free radicals within theadhesion promoter and low dielectric constant polymer layers withhydrogen atoms, thus helping to prevent unwanted reactions with water,oxygen or other free radical scavengers after the composite film on thesubstrate is removed from the deposition chamber and exposed to ambient.

Annealing composite polymer dielectric film 10 may also cause variouschemical changes to occur to the first and second adhesion promoterlayers. Some examples of possible chemical changes are shown in FIG. 2e. For example, the hydrocarbon chain 30 disposed between the silanefunctional group and the acrylo functional group may decompose intogaseous hydrocarbons at a temperature of around 300 degrees Celsius. TheCO₂ group within the acrylo functional group and the terminal *CH₂radical may decompose around 250 degrees Celsius. The ethoxidefunctional groups may leave as ethanol at 300 to 350 degrees Celsius.The loss of these various functional groups during an annealing processoffers the advantage that oxygen is removed from the first and secondadhesion promoter layers. The removal of the oxygen at this stage in adevice fabrication process may help to prevent problems caused by theoxygen in later device fabrication stages, including but not limited tothe formation of bubbles in other layers by oxygen released by laterheating stages However, the loss of these functional groups may causesome of the direct covalent linkages between low dielectric constantpolymer film 16 and substrate 12 (via first adhesion promoter layer 14)to be broken. For example, before annealing composite polymer dielectricfilm 10, the composite dielectric film has a yield strength ofapproximately 50 MPa, which is the tensile strength of the compositepolymer dielectric film and is more than an order of magnitude greaterthan the yield strength in the absence of first adhesion promoter layer14 (2-3 MPa). After annealing, the yield strength of the compositepolymer dielectric film may decrease to around 10 MPa. However, this isstill well above the yield strength required for downstream processes,which is around 4-5 MPa.

The significant yield strength found after annealing may be attributedto the formation of some covalent bonding formed during the annealingprocess by the decomposition reactions shown in FIG. 2 e. FIG. 2 f showsan example of a possible structure that links low dielectric constantpolymer layer 16 to substrate 12 via covalent bonding in first adhesionpromoter layer 14. It will be appreciated that the structure depicted inFIG. 2 f is merely exemplary, and that other structures may also formduring an annealing process.

First adhesion promoter layer 14 and second adhesion promoter layer 18may be formed from any suitable vinyl, keto and/or halide silanematerials, including but not limited to those of the general structures(I)-(IV) set forth above. Silanes of the general structure(RZ)_(x)-Si—((CH₂)₃—O—C═O(CH═CH₂)_(y), have a high sensitivity to UVirradiation, and thus allow a shorter exposure time to be used in theproduction of composite film 10. Other silanes, such as acetylsilanesand vinyl ether silanes, may require a higher energy level of UVirradiation, and therefore may require longer exposure times.

First adhesion promoter layer 14 may be formed from the same silane assecond adhesion promoter layer 18, or may be formed from a differentsilane. Furthermore, while composite polymer dielectric film 10 isdepicted as having both a first adhesion promoter layer 14 and a secondadhesion promoter layer 18, it will be appreciated that the compositedielectric layer may have only one or the other adhesion promoter layer,depending upon whether the adjacent layers in the integrated circuit areable to bond to the low dielectric constant polymer layer 12 withsufficient strength in the absence of an adhesion promoter layer.

Low dielectric constant polymer layer 16 may also be made from anysuitable material, including but not limited to poly(paraxylylene) andfluorinated poly(paraxyxylene) and derivates thereof, and otherpolyaromatics and fluorinated polyaromatics prepared from a monomer ofthe general structure.X′_(m)—Ar—(CZ′Z″Y)_(n)   (V)In this formula, X′ and Y are leaving groups that can be removed to forma free radical for each removed leaving group, Ar is an aromatic groupor a fluorine-substituted aromatic group bonded to in X′ groups and nCZ′Z″Y groups, and Z′ and Z″ are H, F or C₆H_(5-x)F_(x) (x=0, or aninteger between 1 and 5). For example, where m=0 and n=2, removal of theleaving group y from each CZ′Z″Y functional group yields the diradicalAr(CZ′Z″*)₂. Compounds in which Z′ and Z″ are F may have lowerdielectric constants and improved thermal stability. Examples ofsuitable leaving groups for X′ and Y include, but are not limited to,ketene and carboxyl groups, bromine, iodine, —NR₂, —N⁺R₃, —SR, —SO₂R,—OR, ═N⁺═N—, —C(O)N₂, and —OCF—CF₃ (wherein R is an alkyl or aromaticgroup). The numbers in and n in formula (V) may independently be eitherzero or an integer, and (n+m) is equal to or greater than two, but nogreater than the total number of sp² hybridized carbons in the aromaticgroup that are available for substitution.

Ar in formula (V) may be any suitable aromatic group. Examples ofsuitable aromatic groups for Ar include, but are not limited to, thephenyl moiety C₆H_(4-n)F_(n) (n=0 to 4); the naphthenyl moietyC₁₀H_(6-n)F_(n) (n=0 to 6); the di-phenyl moiety C₁₂H_(8-n)F_(n) (n=0 to8); the anthracenyl moiety C₁₂H_(8-n)F_(n) (n=0 to 8 ); thephenanthrenyl moiety C₁₄H_(8-n)F_(n) (n=0 to 8); the pyrenyl moietyC₁₆H_(8-n)F_(n) (n=0 to 8); and more complex combinations of the abovemoieties such as C₁₆H_(10-n)F_(n) (n=0 to 8). Isomers of variousfluorine substitutions on the aromatic moieties are also included. Moretypically, Ar is C₆F₄, C₁₀F₆, or C₆F₄—C₆F₄.

Low dielectric constant polymer film 16 may also be made from aprecursor having the general formulaX′_(m)ArX″_(n)   (VI)wherein X′ and X″ are leaving groups, and Ar is an aromatic orfluorine-substituted aromatic. The numbers m and n each may be zero oran integer, and m+n is at least two, but no greater than the totalnumber of sp² hybridized carbon atoms on Ar that are available forsubstitution. For example, polyphenylene (—(C₆H₄)—) andfluorine-substituted versions thereof may be formed from a precursorhaving general formula (VI). Removal of the leaving groups X′ and/or X″may create the diradical benzyne (*C₆H₄*), which can then polymerize toform polyphenylene. Other aromatic groups besides the phenyl moiety thatmay be used as Ar in formula (VI) include, but are not limited to, thenaphthenyl moiety C₁₀H_(6-n)F_(n) (n=0 to 6); the diphenyl moietyC₁₂H_(8-n)F_(n) (n=0 to 8); the anthracenyl moiety C₁₂H_(8-n)F_(n) (n=0to 8); the phenanthrenyl moiety C₁₄H_(8-n)F_(n) (n=0-8); the pyrenylmoiety C₁₆H_(8-n)F_(n) (n=0-8); and more complex combinations of theabove moieties such as C₁₆H_(10-n)F_(n) (n=0-10).

First adhesion promoter layer 14, low dielectric constant polymer layer16, and second adhesion promoter layer 18 may each have any suitablethickness. Depending upon the materials selected for each layer, thematerial or materials from which first and second adhesion promoterlayers 14 and 18 are formed may have a higher dielectric constant thanthe material from which low dielectric constant polymer layer 16 isformed. In this instance, it may be desirable to utilize relatively thinadhesion promoter layers 14 and 18 compared to the low dielectricconstant layer 16. For example, in some embodiments, the thickness offirst adhesion promoter layer 14 may range from one molecular layer toapproximately 50 angstroms, the thickness of low dielectric constantpolymer layer may range from one molecular layer up to 3000 angstroms,and the thickness of second adhesion promoter layer 18 may range fromone molecular layer to two hundred angstroms. In the specific case of aPPX—F low dielectric constant layer with a thickness of 1500-3000angstroms, a first adhesion promoter layer with a thickness of about 10to 30 angstroms, and a second adhesion promoter layer with a thicknessof about 200 to 500 angstroms, the overall dielectric constant of thecomposite dielectric film is approximately 2.4. It will be appreciatedthat these thickness ranges are merely exemplary, and that firstadhesion promoter layer 14, polymer dielectric layer 16 and secondadhesion promoter layer 18 may have any other suitable thicknesses.

Instead of serving as an adhesion promoter layer, second adhesionpromoter layer 18 may instead (or additionally) be configured to serveas an etch stop for a later etching process in the fabrication of anintegrated circuit, or as a hard mask layer in a single or dualdamascene process. Where second adhesion promoter layer 18 is used as anetch stop layer, it may be desirable to use a somewhat thicker secondadhesion promoter layer 18 than where the second adhesion promoter layeris not used as an etch stop layer.

Where layer 18 is used as a hard mask layer in a damascene process,layer 18 should etch via a similar chemical process, and at similarrates, as low dielectric constant polymer layer 16. In this case, it maybe advantageous for layer 18 to have a lower silicon content. In termsof structure (I) where the silane is an ethoxy silane, a compound of thecomposition (ETO)—Si—(WT)₃ may be used as the hard mask to make theetching characteristics of layer 18 more similar to those of lowdielectric constant polymer layer 16 so that the two layers can beetched by similar chemical processes. Examples of suitable etchingprocesses for these two layers include, but are not limited to, O₂,H₂/N₂, and N₃ etching processes.

On the other hand, where layer 18 is used as an etch stop layer, thesilicon content of layer 18 may be increased so that layer 18 is etchedat a substantially slower rate than low dielectric constant polymerlayer 16. In terms of equation (I) where the silane is an ethoxy silane,layer 18 may have a composition of (ETO)₃—Si—(WT) to give layer 18 asubstantially slower etching rate than layer 16 for O₂, H₂/N₂, and NH₃etching processes. On the other hand, a high silicon-content layer 18may be etched relatively quickly with etching chemistries used forsilicon, such as an SF₄ etching process.

Composite polymer film 10 may be formed in any suitable manner. FIG. 3shows, generally at 100, one exemplary method of forming compositepolymer dielectric film 10. Method 100 includes, at 102, first exposinga substrate on which the composite film is to be formed to UV light.Exposing the substrate to UV light removes water from the substratesurface, and helps first adhesion promoter layer 14 to adhere morestrongly to the substrate surface. Prior methods of removing water fromthe surface of the substrate include drying the wafer surface with adesiccant, and with a combination of desiccation and heat. It has beenfound that exposing the substrate to UV light for just a few secondhelps to achieve the same improvements in adhesion as desiccating thesubstrate for approximately eight hours, or desiccating and heating thesubstrate for approximately six hours. Furthermore, it has been foundthat PPX—F deposited directly onto the surface of the substrate (withoutuse of first adhesion promoter layer 14) after exposing the substrate toUV light has a yield strength of approximately 3-4 MPa. This is asufficiently high yield strength to withstand integrated circuit laterprocessing steps. However, the use of first adhesion promoter layer 14provides a much higher yield strength, and therefore provides a muchlarger margin of safety in a device fabrication process.

After exposing the substrate to UV light at 102, method 100 nextincludes depositing a first layer of silane onto the substrate at 104.The silane may be a material configured to chemically bond both to thesubstrate and to a later-deposited low dielectric constant polymer film,including but not limited to the vinyl, keto and halide silanes listedabove. The silane may be deposited in any suitable manner. For example,the silane may be deposited by flowing an inert carrier gas, such asnitrogen, containing a concentration of the silane across the surface ofthe substrate. Alternatively, the first layer of silane may be appliedby spin-on coating of a solution of the silane in a solvent such asisopfopyl alcohol. The substrate may be held at any suitable temperaturewhile the silane is deposited. In some embodiments, the substrate isheld between approximately zero and −20 degrees Celsius duringdeposition of the silane in order to increase the adsorption rate andincrease system throughput for the deposition of composite film 10.Furthermore, the first layer of silane deposited at 104 may be depositedin a layer of any desired thickness. For example, the silane may bedeposited to a thickness of between one molecular layer andapproximately 30 angstroms, or may be deposited in a layer thicker than30 angstroms where suitable.

After depositing the first layer of silane at 104, the first layer ofsilane is exposed to a free radical-generating energy source, such as UVlight, at 106. Exposure to the free radical-generating energy source at106 generates free radicals from the silane, and may initiatepolymerization of the first adhesion promoter layer, for example, if thesilane is an acrylo silane. The UV lamp may output UV light of anysuitable wavelength, including but not limited to wavelengths between170 nm and 350 nm. More specifically, wavelengths between 220 and 300 nmmay optionally be employed to help to avoid the formation of ozone.

If desired, the amount of UV energy to which the first silane layer isexposed may be limited to only partially polymerize the layer. This mayresult in the formation of a larger number of unreacted CH* and CH₂*radicals for reacting with a subsequently-formed low dielectric constantpolymer layer. While the free radical-generating energy source isdepicted in FIG. 3 as being a UV lamp, it will be appreciated that anyother suitable type of energy source may be used. Examples include, butare not limited to, thermal sources, especially if the silane is asilane. In either case, exposure to the free radical-generating energysource may be performed in the absence of free radical scavengers,including but not limited to oxygen, water, and amino-containingcompounds. This may help to avoid growing polymer chains from beingterminated by the free radical scavengers. The resulting silane polymersinclude many pending Si(ZR)_(x) groups that may bond to the underlyingsilicon-containing substrate, and also free radical chain ends —H₂C*capable of reacting with low dielectric constant polymer layer 16.

Next, low dielectric constant polymer film 16 is formed by depositing,at 108, a gas-phase diradical monomer onto first adhesion promoter layer14. During this process, the substrate may be cooled sufficiently tocause the gas phase diradical monomer molecules to condense on firstadhesion promoter layer 14. However, the substrate should not be cooledto such an extent that the gas phase diradical monomer molecules toimmediately stick to adhesion promoter layer 14 in any orientation.Instead, the substrate should be cooled to a temperature that allows thegas phase diradical monomer molecules to have sufficient energy to“bounce” on the surface of the first adhesion promoter layer so that themonomer diradical molecules can find an energetically favorableorientation. This may allow the low dielectric constant polymer layer togrow with a relatively high degree of crystallinity. Suitabletemperature ranges for achieving this effect may differ depending uponthe monomer being deposited. However, in general, temperatures below themelting temperature of the diradical intermediates or the growing lowdielectric constant polymers are suitable for achieving this effect. Forthe diradical monomer *CF₂C₆H₄CF₂*, suitable temperatures may includethose between approximately −30 and −50 degrees Celsius.

It has been found that, with the temperature held at a suitable level,PPX—F can be deposited from the gas phase diradical monomer *CF₂C₆H₄CF₂*with an initial crystallinity of 20-50% in a β₂ phase of the material.Furthermore, it has been found that the polymer chains having the 20-50%initial crystallinity have a high degree of alignment along a singlecrystallographic direction, and that the crystallinity can thus beincreased to 70% simply by annealing the film at a temperature higherthan the glass transition temperature (approximately 170 degrees Celsiusfor PPX—F), but lower than the melting temperature of the polymer, forintervals as short as three minutes or less. The low dielectric constantpolymer film formed at 108 may be annealed before the second layer ofsilane material is deposited, or may be annealed after all layers ofcomposite polymer dielectric film 10 have been deposited, as describedbelow.

Next, the second layer of silane is deposited onto the polymerdielectric layer at 110. This layer is then exposed to UV light at 112to initiate polymerization of the silane molecules to form the secondadhesion promoter layer 18 (or an etch stop or hard mask layer), and toreact the second adhesion promoter layer, the etch stop or the head masklayer with low dielectric constant polymer layer 16. The second silanelayer may be deposited in any suitable thickness As described above,where second silane layer 18 is to be used as an etch-stop or hard masklayer, the second silane layer may be applied in a thicker layer rangingfrom 200 to 500 angstroms. Likewise, the second silane layer may beapplied in a thinner layer ranging from 5 to 20 angstroms when layer 18is not to be used as an etch-stop or hard mask layer to reduce theimpact of the second adhesion promoter layer on the overall dielectricconstant of the structure.

The second silane layer may be deposited in any suitable manner,including but not limited to vapor phase deposition techniques, eitherwith or without a carrier gas, and spin-on deposition techniquesutilizing a solution of silane in a suitable solvent.

After depositing the second layer of silane onto the low dielectric at110 and exposing the second layer of silane to UV light (or other freeradical-generating energy source) at 112, the composite polymerdielectric film may be annealed in the presence of a reducing gas, suchas hydrogen, at 114. After formation of the composite polymer dielectricfilm, many unreacted free radicals *CH, *CH₂, and *CF₂ may remain in thelayers making up the composite film. Annealing in the presence ofhydrogen may eliminate these free radicals before composite polymerdielectric film 10 is removed from the deposition system environment toavoid reactions with water, oxygen or nitrogen compounds that may causeproblems in later processing stages. Furthermore, annealing in thepresence of hydrogen may help to increase the number of Si-Z-Si bondsthat are formed between the silane end of the silane molecule andadjacent silicon-containing layers. Annealing also may help to improvethe crystallinity of the low dielectric constant polymer layer. Forexample, as described above, the crystallinity of the polymer chains ofthe low dielectric constant polymer material may improved from 20-50% toabout 70% during this annealing step.

Composite polymer dielectric film 10 may be annealed at any suitabletemperature, and under any suitable concentration of hydrogen and/ormixture of hydrogen with other inert gases such as noble gases.Depending upon the temperature regime used, nitrogen may not be suitablefor this process, as nitrogen may react with radicals in the compositefilm under annealing conditions. Examples of suitable annealingtemperatures include, but are not limited to, temperatures sufficient topromote the reactions of free radicals in the composite polymer filmwith hydrogen, yet that are below the melting points of the lowdielectric constant polymer layers. In the specific case of a compositefilm formed from an acrylic or methacrylic silane and PPX—F, annealingtemperatures of between 300 and 400 degrees Celsius may be sufficient toeliminate free radicals within composite polymer dielectric film 10, andto increase the crystallinity of the PPX—F layer and to create achemically, electrically and dimensionally stabilized film.

Composite polymer dielectric film 10 may be annealed under any suitablepressure and concentration of hydrogen. For example, composite polymerdielectric film 10 may be annealed under pure hydrogen gas (of anysuitable purity), or may be annealed under hydrogen gas diluted inanother inert gas. Examples of suitable diluent gases include, but arenot limited to, inert gases such as argon or helium. The total pressurewhile annealing composite polymer dielectric film 10 may be betweenapproximately 200 mTorr to 500 Torrs, and more typically betweenapproximately 1 to 20 Torrs.

Likewise, composite polymer dielectric film 10 may be heated using anysuitable heat source. For example, a hotplate may be used to heatcomposite polymer dielectric film 10 during annealing, or an indirectradiative heat source may be used.

Composite polymer electric film 114 may be annealed under hydrogen forany suitable amount of time. For example, in the specific case of acomposite film formed from an acrylic or methacrylic silane and PPX—Fannealed at a temperatures of between 300 and 400 degrees Celsius, anannealing time of between 2 and 10 minutes on a hot plate may besufficient to eliminate free radicals and to increase the crystallinityof the PPX—F layer.

While the embodiment of FIG. 3 shows both the first silane layer and thesecond silane layer as being individually exposed to a freeradical-generating energy source after the layers are deposited, it willbe appreciated that polymerization of either the first silane layer, thesecond silane layer, or both the first and second silane layer may beinitiated after all three layers have been deposited. In this instance,heat may be applied to the composite dielectric polymer film in theabsence of hydrogen (arid any free radical scavenging species) for afirst interval to cause reaction with low dielectric constant layer 16and, depending upon the chemical properties of the silane material,polymerization of these layers, and then heat may be applied for asecond interval in the presence of hydrogen to eliminate any remainingfree radicals.

As described above, even in the absence of first adhesion promoter layer14, the adhesion of low dielectric constant polymer layer 16 may beimproved by exposing the substrate to UV light for a brief intervalbefore exposing the substrate to the diradical monomer to create the lowdielectric constant polymer layer. FIG. 4 shows, generally at 200, anembodiment of a method of forming a low dielectric constant polymer filmin this manner. Method 200 includes first, at 202, exposing thesubstrate to UV light to remove water (and possibly other contaminants)from the surface of the substrate. The substrate may be exposed to anysuitable wavelength of UV light, and for any suitable interval. Forexample, the substrate may be exposed to UV light between 170 nm and 350nm, or more specifically between 220 and 300 nm.

After exposing the substrate to UV light at 202, the substrate may nextbe exposed at 204 to a gas phase diradical monomer, such as onegenerated from the compounds disclosed above in structures (V) and (VI),to form the low dielectric constant polymer layer. The substrate may bemaintained in a high vacuum environment between exposure to the UV lightat 202 and exposure to the gas phase diradical monomer at 204 to preventthe substrate surface from being re-contaminated by water or othercontaminants. To maintain a sufficiently pure environment duringdeposition, the deposition system may be configured to have a leakagerate of less than approximately 2 mTorr/minute, and more specificallyless than about 0.4 mTorr/min. After completing the growth of the lowdielectric constant polymer film at 204, the low dielectric constantpolymer layer may be annealed in the presence of hydrogen, as describedabove in the context of FIG. 3.

FIG. 5 shows, generally at 300, a block diagram of an exemplary systemfor forming composite dielectric polymer system 10. System 300 isdescribed in the context of a system for depositing a PPX-based polymer,but it will be appreciated that system 300 may be adapted for use withany other suitable low dielectric constant polymer film. System 300includes one or more process modules 302 (a second process module isshown generally at 302 a), a post-treatment module 304, a transfermodule 306 connecting the process module 302 and the post-treatmentmodule 304, an equipment front-end module 308 (EFEM) that interfacessystem 300 with an exterior environment, and first and second load locks310 and 312 for respectively introducing substrates into and removingsubstrates from transfer module 306.

System 300 also has a system controller 314 including memory 316 havinginstructions stored thereon that are executable by a processor 318 forcontrolling the various parts of system 300 to effect the formation ofcomposite polymer dielectric film 10. Controller 314 is depicted in FIG.5 as having electrical connections to a process module controller 314 aon process module 302, a post-treatment controller 314 b onpost-treatment module 304, and to transfer module 306 (which may alsoinclude its own controller, not shown). However, it will be appreciatedthat controller 314 may have electrical connections to any othercomponent having electrical systems, including but not limited to loadlock 310, load lock 312, equipment front end module 308, and anysub-components contained within the general components shown in FIG. 5.The depicted system configuration allows all three layers of compositepolymer dielectric film 10 to be deposited and annealed without breakingthe deposition vacuum, and thus achieving high system throughputs whileincreasing manufacturing yields.

It will be appreciated that the electrical portion of FIG. 5 merely setsforth an exemplary hardware architecture, and does not indicate aparticular physical relationship between the system controller andindividual module controllers. Moreover, it will be appreciated that thedepicted hardware architecture is merely exemplary, and that system 10may utilize any other suitable architecture. For example, a singlecontroller may be used to control all functions of all modules, ratherthan having a controller for each module. Furthermore, while only systemcontroller 314 is depicted as having memory and a processor, each of theindividual module controllers typically also has memory and one or moreprocessors associated therewith.

Process module 302 is configured to form first adhesion promoter layer14, low dielectric constant polymer layer 16, and second adhesionpromoter layer 18. Process module 302 includes a silane delivery system319 with a silane container 320 and a carrier gas source 322 (typicallynitrogen or other suitable inert gas) fluidically connected with thesilane container via a mass flow controller 324. Process module 302 alsoincludes a gas phase monomer delivery system 325, described in moredetail below.

Silane delivery system 319 is configured to deliver a flow of a silaneinto a deposition chamber 326 for forming first adhesion promoter layer14 and second adhesion promoter layer 18 on a substrate in thedeposition chamber. In addition to mass flow controller 324, variousvalves (not shown) may be disposed between silane container 320 anddeposition chamber 326 to regulate the flow of into the depositionchamber.

System controller 314 electronically communicates with process modulecontroller 314 a to start and finish the silane deposition process,while process module controller 314 a directs process module 302 toperform the various functions and operations that produce layers 14, 16and 18 of composite polymer dielectric film. For example, process modulecontroller 314 a maintains the clean vacuum environment for depositionchamber 326 and reactor 338 via a vacuum pump system (not shown),controls the temperature distribution of the heating elements 332,delivers a desired amount of PPX precursor from precursor canister 334into deposition chamber 326 through vapor flow controller 336 andreactor 338, and effects the UV lamp 330 to remove water from thesubstrate surface, etc.

To effect the silane deposition process, process module controller 314 amaintains a desired gas pressure and mixture within the depositionchamber 326. For example, the base pressure within deposition chamber326 may be held below 0.5 mTorr, and more specifically below 0.05 mTorrand during deposition of the silane at 200 mTorr to 500 Torrs,preferably between 2 to 20 Torrs. Alternatively, higher pressures may beemployed.

Process module controller 314 a may introduce silane precursor intodeposition chamber 326 at any suitable rate. The rate and/or amount ofsilane that is introduced into deposition chamber 326 may be controlledby controlling the temperature of the silane container (which affectsthe vapor pressure of gas phase silane in the container) and the flowrate of nitrogen into the deposition chamber 326. Examples of suitablesilane temperatures and nitrogen flows include temperatures in the rangeof 10 and 50 degrees Celsius, and flow rates between 50 and 500 sccm,although silane temperatures and nitrogen flow rates outside of theseranges may also be used. It will be appreciated that silane container320 may include various heaters, temperature controllers, leveldetectors, and other components electrically coupled to and controlledby controller 314 that are not shown in the high-level block diagram ofFIG. 5. Likewise, other components shown in FIG. 5 may include variousdetectors, pumps, temperature control systems, etc. that have beenomitted from FIG. 5 for purposes of clarity.

Deposition chamber 326 may include a temperature-controlled chuck 328for maintaining a substrate at a controlled temperature within thechamber. Temperature-controlled chuck 328 may be an electrostatic chuck,and may include a gas outlet configured to allow a desired pressure of aheat transfer gas to be maintained between the substrate and chucksurface, thus helping to maintain the substrate surface at asubstanitially uniform temperature. For example, maintaining helium at apressure of up to 10 psi between the substrate and chuck has been foundto keep the temperature across the surface of the substrate within onedegree Celsius of a desired target temperature. Furthermore, the use ofan electrostatic chuck as temperature-controlled chuck 328 may providesufficient holding force between the chuck and the substrate to keep theleak rate for helium below 0.4 sccm.

Deposition chamber 326 may also include a UV lamp 330 configured toilluminate a substrate positioned on temperature-controlled chuck 328.UV lamp 330 may be used both to remove water (and other contaminants)from a substrate surface prior to depositing any film layers on thesubstrate, and also may be used to cause the free radical polymerizationof the adhesion promoter layers and the chemical bonding of the adhesionpromoter layers with the low dielectric polymer layer. Depositionchamber 326 may, alternatively or additionally, include heating elements332 or a plasma source 333 for causing the polymerization of the silanelayers. UV lamp 330 and/or heating elements 332 may be positionedoutside of deposition chamber 326 and irradiate through a quartz (orother UV-transparent material) window provided in the depositionchamber. Alternatively, a suitable UV lamp may be positioned within thedeposition chamber.

Deposition chamber 326 may be configured to have a low leakage rate andto hold a high vacuum to help avoid the introduction of free radicalscavenger species, such as oxygen and amino-containing compounds, duringthe various layer deposition and polymerization processes. For example,deposition chamber 326 may be configured to hold a Vacuum of less than0.01 mTorr during the deposition of the low dielectric constant polymerlayer, and have a leakage rate of less than approximately 2mTorr/minute, and in some embodiments, as low as 0.4 mTorr/minute orless.

Process module 302 also includes a gas phase monomer delivery system 325for delivering a low dielectric constant polymer free radicalintermediate to deposition chamber 326. Gas phase monomer deliverysystem 325 includes a precursor vessel 334 for holding a precursormaterial, a vapor flow controller 336 for regulating the flow of vaporphase precursor out the vessel, and a reactor 338 for creating a gasphase free radical intermediate from the precursor. For example, wherethe precursor is the monomer CF₂BrC₆H₄CF₂Br, reactor 338 may convert theprecursor to the diradical *CF₂C₆H₄CF₂* for the formation of a PPX—Ffilm. Furthermore, reactor 338 may be configured to chemically reactwith the bromine leaving groups and to be periodically regenerated toremove bromine from the reactor. Examples of suitable reactors includethose disclosed in U.S. patent application Ser. No. 10/243,990 of Lee etal., filed Sep. 13, 2002, the disclosure of which is incorporated byreference.

Process module controller 314 a may be configured to maintain precursorvessel 334 at any suitable temperature for producing a desired vaporpressure of precursor monomer. For example, where BrCF₂C₆H₄CF₂Br is themonomer precursor, process module controller 314 a may maintainprecursor vessel 334 at a temperature of between approximately 40 and 90degrees Celsius to create a sufficient vapor pressure of the monomer.Likewise, process module controller 314 a may be configured to maintainany suitable rate of flow of vapor phase precursor into reactor 338 viavapor phase controller 336. Examples of suitable flow rates of precursorinto reactor 338 include, but are not limited to, flow rates of between1 and 50 sccm, ±1 sccm.

As mentioned above, system 300 may include one or more process modules302. While the embodiment depicted in FIG. 5 includes two processmodules 302, it will be appreciated that system 300 could include threeor more process modules if desired. The use of multiple process modulesmay help to increase substrate throughput. Alternatively, a designatedprocess chamber for deposition of the first and second silane layers canalso be employed where more than two process modules are included in adeposition system, as described in more detail below.

Post-treatment module 304 is configured to perform the above-describedpost-deposition heating and/or annealing processes. Furthermore,post-treatment module 304 may be configured to perform the deposition offirst adhesion promoter layer 14, second adhesion promoter layer 18, orboth adhesion promoter layers instead of (or in addition to) processmodules 302 and 302 a. Post-treatment module 304 includes an annealinggas source 340, at least one valve 342 to control a flow of annealinggas from the annealing gas source 340 into a processing chamber 344, andone or more heating elements 346 for heating a substrate during anannealing process.

Processing chamber 344 may be configured to process substrates one at atime, or may be equipped for batch processing, with such features as awafer elevator 348, etc., where equipped for batch processing,processing chamber 344 may include a plurality of heating elements 346to provide consistent heating to each of a plurality of wafers beingprocessed. The use of a wafer elevator 348 allows a plurality ofsubstrates in processing chamber 344 to be vertically stacked, which mayhelp to reduce the footprint of processing chamber 344 relative to abatch processor in which the substrates are not vertically stacked. Thenumber of heating elements 346 and the height of wafer elevator 348 isdetermined at least in part by the number of process modules 302 used insystem 300.

Processing chamber 344 of post-treatment module 304 may be configured tohave a low leakage rate and be able to hold a high vacuum to help avoidthe introduction of free radical scavengers such as O₂ and H₂O fromoutside of the chamber. Examples of suitable leak rates for processingchamber 344 of post-treatment module 304 include, but are not limitedto, rates below about 2 mTorr/minute. Heating elements 346 ofpost-treatment module 304 may be radiant heaters, one or more hotplateson which substrates rest during processing, or may take any othersuitable form. Heating elements 346 are controllable by controller 314to heat a substrate to any suitable temperature for annealing. In thespecific case of a PPX—F low dielectric constant polymer film, theheating elements may be configured to heat the substrates to a constantcontrolled temperature of between approximately 300-450 (±2-5) degreesCelsius.

Post-treatment module 304 may also be configured to deposit firstadhesion promoter layer 14 and/or second adhesion promoter layer 318. Inthis instance, post-treatment module 304 may include a silane precursordelivery system 350 configured to deliver a flow of silane precursorinto processing chamber 344 for forming first adhesion promoter layer 14and second adhesion promoter layer 18. Silane precursor delivery system350 may be similar in structure and function to silane precursordelivery system 319 described above in the context of process module302. Post-treatment module 304 also may include a UV lamp (or other freeradical-generating energy source, such as a plasma source) forpolymerizing the silane precursor.

Post-treatment module controller 314 b directs post-treatment module 304to perform the various functions and operations that go into thepost-deposition processing of composite polymer dielectric film 10. Forexample, post-treatment module controller 314 b regulates the compositefilm annealing temperature through heating elements 346, maintainsprescribed hydrogen/helium pressure within processing chamber 344 viathe gas source 340 and controlling valve 342, and controls the verticalindexing motion of the wafer elevator 348 for wafer transfer into andout of post-treatment module 304. System controller 314 may communicatewith post-treatment module controller 314 b to cause the post-treatmentmodule controller to start and stop these processes.

Transfer module 306, equipment front end module 308, load lock 310 andload lock 312 each may be considered part of a platform that supportsuse of process module(s) 302 and post-treatment module 304. During adeposition process, a substrate is loaded initially into equipmentfront-end module 308, where alignment systems within the equipmentfront-end module pre-align the substrate. The substrate is then movedvia a mechanical arm or other transfer apparatus (not shown in FIG. 5)within equipment front-end module 308 to load lock 310, which is pumpeddown to a pressure of a few mTorr. From load lock 310, another substratetransfer apparatus (not shown in FIG. 5) within transfer module 306transfers the substrate from load lock 310 into the transfer module, andthen into the silane deposition module for an initial exposure to UVlight and/or deposition of the first adhesion promoter layer.

Transfer module 306 is also controllable by controller 314 to transfer asubstrate among process module(s) 302 and post-treatment module 304 atappropriate times during the manufacture of composite dielectric polymerfilm 10. To help prevent reaction of unreacted free radicals incomposite dielectric film with free radical scavengers while thesubstrate is being transferred between process module(s) 302 andpost-treatment module 304, transfer module 306 may be maintained at asuitable level of vacuum. Suitable levels of vacuum include, but are notlimited to, pressures below 0.1 mTorr. Maintaining transfer module 306at pressures in this range may help to avoid the introduction of harmfulquantities of free radical scavengers into transfer module 306, and thusmay help to prevent unwanted reactions.

Once all processing steps have been completed, transfer module 306 maybe controlled by controller 314 to transfer a substrate into load lock312, where it may be brought back to the pressure of equipment front-endmodule 308 for removal from system 300.

FIG. 6 shows, generally at 400, a block diagram of another exemplarysystem for forming composite dielectric polymer system 10. Like system300, system 400 includes one or more process modules 402 (a secondprocess module is shown generally at 402 a), a post-treatment module404, a transfer module 406 connecting the process module 402 and thepost-treatment module 404, an equipment front-end module 408 (EFEM) thatinterfaces System 400 with an exterior environment, and first and secondload locks 410 and 412 for respectively introducing substrates into andremoving substrates from transfer module 406. System 400 also includes asystem controller 414 including memory 416 having instructions storedthereon that are executable by a processor 418 to control the variousfunctions of system 400. System controller 414 may interface withseparate module controllers 414 a, 414 b, which control the individualfunctions of each module.

System 400 also includes a separate silane deposition module 420 fordepositing layers 14 and 18 of composite polymer dielectric film 10.Silane deposition module 420 includes a silane deposition chamber 422 towhich a silane delivery system 424 is connected. Silane delivery system424 is configured to deliver a flow of a silane into silane depositionchamber 422 for forming first adhesion promoter layer 14 and secondadhesion promoter layer 18 on a substrate positioned in the silanedeposition chamber. Silane delivery system 424 includes a silanecontainer 426 and a carrier gas source 428 (typically nitrogen or othersuitable inert gas) fluidically connected with the silane container viaa mass flow controller 430. Other valves may be disposed between silanecontainer 426 and silane deposition chamber 422 preventing or allowingsilane to flow into the silane deposition chamber.

Silane deposition chamber 422 may include a free radical-generatingenergy source for creating free radicals in the silane molecules toallow the polymerization of the silane molecules, and reactions betweenthe silane molecules and the low dielectric constant polymer layer. Oneexample of a suitable free radical generating source is a UV lamp 425.UV lamp 425 may also be used to remove water from substrate surfacesprior to depositing layer 14 of composite polymer dielectric film 10.Alternatively, another energy source, such as a plasma source 427 or athermal energy source, may be used.

Silane deposition module 420 also includes a silane deposition modulecontroller 414 c for controlling the various processes and operations ofthe silane deposition process, including but not limited to the deliveryof silane precursor from the silane canister to the deposition chamber,and the temperature of temperature controlled chuck. System controller414 electronically communicates with silane deposition module controller414 c to start and finish the silane deposition process. To effect thesilane deposition process, silane deposition module controller maintainsthe gas pressure of the silane deposition chamber, the temperature ofthe silane precursor, the flow of the carrier gas, etc. For example, thebase pressure within silane deposition chamber may be held below 0.5mTorr, and more specifically below 0.05 mTorr. During deposition of thesilane, pressure within silane deposition chamber 424 may be held at apressure of between approximately 200 mTorr and 500 Torrs, and morespecifically between 2 to 20 Torrs. Alternatively, higher pressures maybe employed.

Silane deposition module controller 414 c may be configured to introducesilane into silane deposition chamber at any suitable rate. Examples ofsuitable silane temperatures and nitrogen flows include temperatures inthe range of 10 and 50 degrees Celsius, and flow rates between 50 and500 sccm, although silane temperatures and nitrogen flow rates outsideof these ranges may also be used. It will be appreciated that silanecontainer 320 may include various heaters, temperature controllers,level detectors, and other components electrically coupled to andcontrolled by silane deposition module controller that are not shown inthe high-level block diagram of FIG. 6. Likewise, other components shownin FIG. 6 may include various detectors, pumps, temperature controlsystems, etc. that have been omitted from FIG. 6 for purposes ofclarity.

While the depicted silane deposition module includes only a singlesilane delivery system, it will be appreciated that the silanedeposition module may include plural silane delivery systems. Forexample, where first adhesion promoter layer 14 is made of a silanehaving the general formula (ETO)₃—Si—(WT) while third adhesion promoterlayer 18 is made of a silane having the general formula (ETO)—Si—(WT)₃,the silane deposition module may have a separate silane delivery systemfor each of these silanes.

FIG. 7 shows, generally at 500, a plan view of an embodiment of aprocessing system for forming composite dielectric film 10 arranged on afabrication room floor. System 500 includes three process modules 502,one post-treatment module 504, and one silane deposition module 520. Atransfer module 506 is disposed in a central location, and the processmodules 502, post-treatment module 504, and load locks 310 and 312 aredisposed around the transfer module. Transfer module 506 includes apivotal mechanical arm 508 configured to transfer a wafer between waferconveyors 522 and 524 on load locks 510 and 512, respectively, waferconveyors 526, 528 and 530 on process modules 502, and wafer conveyor532 on post-treatment module 304. The depicted configuration of system500 allows a substrate to be transferred between load locks 510 and 512,transfer module 506, process modules 502, post-treatment module 504without breaking the overall system vacuum. Substrates may besequentially processed in process modules 502, and then annealed inpost-treatment module 504 in a batch manner for a high systemthroughput. Using the above-disclosed processing equipment andconditions, composite polymer dielectric film 10 can be deposited andannealed on a wafer in 4 to 6 minutes, which is within the timetolerances dictated by the overall fabrication speed of typicalintegrated circuit processing lines. It will be appreciated that theconfiguration shown in FIG. 7 is merely exemplary, and that any othersuitable arrangement of the various components of systems 300 and/or 400may be used.

Although the present disclosure includes specific embodiments of variouscomposite dielectric films, methods of forming the films, and systemsfor forming the films, specific embodiments are not to be considered ina limiting sense, because numerous variations are possible. The subjectmatter of the present disclosure includes all novel and nonobviouscombinations and subcombinations of the various films, processingsystems, processing methods and other elements, features, functions,and/or properties disclosed herein. The following claims particularlypoint out certain combinations and subcombinations regarded as novel andnonobvious. These claims may refer to “an” element or “a first” elementor the equivalent thereof. Such claims should be understood to includeincorporation of one or more such elements, neither requiring norexcluding two or more such elements. Other combinations andsubcombinations of features, functions, elements, and/or properties maybe claimed through amendment of the present claims or throughpresentation of new claims in this or a related application. Suchclaims, whether broader, narrower, equal, or different in scope to theoriginal claims, also are regarded as included within the subject matterof the present disclosure.

1. A system for depositing a composite polymer dielectric film on a substrate, the composite polymer dielectric film including a low dielectric constant polymer layer disposed between and chemically bonded to a first silane-containing layer and a second silane-containing layer, the system comprising: a process module including a processing chamber and a monomer delivery system configured to deliver a gas-phase monomer into the processing chamber for deposition of the low dielectric constant polymer layer; a post-treatment module for annealing the composite polymer dielectric film; a silane delivery system configured to deliver a vapor flow containing a silane precursor into the system for forming the first silane-containing layer and the second silane-containing layer; and memory and a processor in electrical communication with the process module, the post-treatment module and the silane delivery system, wherein the memory includes instructions stored thereon executable by the processor to deposit the silane precursor on the substrate for a first interval to form the first silane-containing layer, deposit the gas phase monomer on the first adhesion promoter layer for a second interval to form the low dielectric constant polymer layer, and deposit the silane precursor on the low dielectric constant polymer layer for a third interval to form the second silane-containing layer.
 2. The system of claim 1, wherein the silane delivery system is configured to deliver the silane precursor to a silane deposition module that includes a silane deposition chamber and a free radical-generating energy source, and wherein the instructions are executable by the processor to control an exposure of the silane precursor to energy from the energy source to form free radicals in the silane precursor after depositing the silane precursor on the substrate for the first interval.
 3. The system of claim 2, wherein the free-radical generating energy source is a UV light source.
 4. The system of claim 2, wherein the free-radical generating energy source is a thermal energy source.
 5. The system of claim 2, wherein the free-radical generating energy source is a plasma source.
 6. The system of claim 1, wherein the silane delivery system is configured to deliver the silane precursor to the process module.
 7. The system of claim 1, wherein the silane delivery system is configured to deliver the silane precursor to the post-treatment module.
 8. The system of claim 1, wherein the post-treatment module includes a heater for heating the substrate, and wherein the instructions are executable by the processor to anneal the composite dielectric layer in a presence of hydrogen in the post-treatment module via the heater after depositing the silane precursor on the low dielectric constant polymer layer for the third interval.
 9. The system of claim 8, wherein the heater is a hot plate.
 10. The system of claim 8, wherein the instructions are executable by the processor to anneal the composite dielectric layer in a presence of 3-10% H₂ in He.
 11. The system of claim 8, wherein the instructions are executable to anneal the composite dielectric layer at a temperature of between approximately 250 and 450 degrees Celsius.
 12. The system of claim 8, wherein the instructions are executable to anneal the composite dielectric layer for a duration of between approximately 2 and 10 minutes.
 13. The system of claim 1, wherein the process module includes a cooled substrate holder, and wherein the instructions are executable to hold the substrate at a temperature below the crystallization temperature of low dielectric constant polymer layer while depositing the gas phase monomer.
 14. The system of claim 13, wherein the instructions are executable to hold the substrate at a temperature of between approximately −25 and −55 degrees Celsius while depositing the gas phase monomer.
 15. The system of claim 13, wherein the cooled substrate holder is an electrostatic chuck.
 16. The system of claim 15, the chuck having a surface, wherein up to 10 psi of helium is disposed between the substrate and the surface of the chuck during substrate cooling to aid in cooling the substrate.
 17. The system of claim 1, wherein the instructions are executable to hold the substrate at a temperature of approximately 25 degrees Celsius or below when depositing the silane precursor.
 18. The system of claim 1, wherein the post-treatment module includes an annealing chamber, a vacuum pump system, a mass flow controller, and at least one valve controlling a flow of gas into the annealing chamber, and wherein the instructions are executable to hold an atmosphere within the annealing chamber at a pressure of between approximately 1 and 10 Torr via the vacuum pump and the valve.
 19. The system of claim 1, wherein the post-treatment module includes a substrate elevator and a plurality of heating elements for batch substrate processing.
 20. The system of claim 1, wherein the first silane-containing layer is a first adhesion promoter layer configured to chemically bond to an underlying silicon-containing layer.
 21. The system of claim 1, wherein the second silane-containing layer is a hard mask layer.
 22. The system of claim 1, wherein the second silane-containing layer is an etch stop layer.
 23. The system of claim 1, wherein the second silane-containing layer is a second adhesion promoter layer configured to chemically bond to an overlying silicon-containing layer.
 24. A system for depositing a composite polymer dielectric film on a substrate, the composite polymer dielectric film including a low dielectric constant polymer layer disposed between a first adhesion promoter layer and an overlayer, wherein the overlayer includes at least one layer selected from the group consisting of a second adhesion promoter layer, an etch stop layer and a hard mask layer, wherein the first adhesion promoter layer includes reactive silane groups configured to chemically bond to a silicon-containing layer that is in contact with the adhesion promoter layer, the system comprising: a process module for forming the low dielectric constant polymer layer, wherein the process module includes a deposition chamber and a substrate holder configured to hold and cool a substrate during a deposition process; a monomer delivery system for delivering a gas-phase diradical monomer to the deposition chamber; a post-treatment module for annealing the composite polymer dielectric film, wherein the post-treatment module includes a heat source for heating the substrate and processing gas delivery system for delivering a reducing gas to the post-treatment module; a silane deposition module for depositing the first adhesion promoter layer and the overlayer, wherein the silane deposition module includes a silane deposition chamber and a silane delivery system for delivering a silane precursor to the silane deposition chamber; and a transfer module disposed between the process module, the silane deposition module and the post-treatment module, wherein the transfer module includes a substrate transport mechanism for transferring a substrate between the process module and the post-treatment module.
 25. The system of claim 24, wherein the silane deposition module includes at least one of a UV light source, a heater and a plasma source to generate free radicals in the silane precursor.
 26. The system of claim 24, wherein the silane deposition module includes a plurality of silane delivery systems for delivering a plurality of silane compounds to the silane deposition chamber.
 27. The system of claim 24, wherein the substrate holder includes a cooling mechanism configured to cool the substrate when the substrate is in the holder.
 28. The system of claim 27, wherein the substrate holder is an electrostatic chuck configured to allow a pressure of 10 psi or less of helium to be held between the chuck and the substrate to aid in cooling the substrate.
 29. The system of claim 24, wherein the monomer delivery system includes a vessel configured to hold a precursor to the gas-phase diradical, and a reactor configured to generate the diradical from the precursor.
 30. The system of claim 29, wherein the monomer delivery system includes a vapor flow controller disposed between the vessel and the reactor.
 31. The system of claim 24, wherein the silane delivery system includes an inert gas supply, a mass flow controller, and a silane vessel for containing and heating a volume of a silane precursor.
 32. The system of claim 24, wherein the post-treatment module includes a hot plate for heating the substrate during annealing.
 33. The system of claim 24, further comprising a first load lock and a second load lock coupled to the transfer module, wherein the first load lock is configured to accept insertion of a substrate into the system, and wherein the second load lock is configured to permit removal of a substrate from the system.
 34. A computer-readable storage medium containing instructions stored thereon, wherein the instructions are executable by a processor on a wafer processing system to direct the wafer processing system to perform a method of forming a composite dielectric film on a wafer, the composite dielectric film including an adhesion promoter layer having a plurality of silane groups, and a low dielectric constant polymer layer disposed on the adhesion promoter layer and chemically bonded to the adhesion promoter layer, the method comprising: depositing a silane material onto the wafer; exposing the silane material to a free-radical generating energy source to generate free-radicals from vinyl, keto or alkyl halide functional groups on the silane material and to form the first adhesion promoter layer; depositing the low dielectric constant polymer layer on the adhesion promoter layer by exposing the wafer to a concentration of a gas phase free radical; and heating the adhesion promoter layer and the polymer dielectric in the presence of hydrogen.
 35. The storage medium of claim 34, wherein the instructions are executable to direct the wafer processing system to deposit the low dielectric constant polymer layer while the substrate is held at a temperature of between approximately −30 and −50 degrees Celsius by a cooled substrate holder.
 36. The method of claim 34, wherein the adhesion promoter layer is a first adhesion promoter layer, and wherein the instructions are executable to direct the wafer processing system to deposit a second adhesion promoter layer on low dielectric constant polymer layer before heating under hydrogen.
 37. The method of claim 36, wherein the instructions are executable to direct the wafer-processing system to expose the second adhesion promoter layer to free-radical generating energy after depositing the second adhesion promoter layer.
 38. The storage medium of claim 37, wherein the free-radical generating energy is UV light.
 39. The storage medium of claim 34, wherein the silane material is selected from materials having a general formula of (RZ)_(x)-Si—(W-T)_(y), wherein W is selected from the group consisting of —O—, —CH₂—, —(CH₂)_(a)C═OO—and —(CH₂)_(a)OO═C—; wherein T is selected from the group consisting of —CR═CR′R″, an alkyl halide, and —RC═O; wherein Z is selected from the group consisting of O and NR; wherein R, R′ and R″ are an H, alkyl or aromatic group; wherein a is 0 or an integer; wherein x=1, 2 or 3; wherein y=1, 2 or 3, and wherein x+y=4.
 40. The method of claim 34, wherein the silane material is selected from materials having a general formula of H_(x)Si—(W-T)_(y), wherein W is selected from the group consisting of —O—, —CH₂—, —(CH₂)_(a)C═OO—, and —(CH₂)_(a)—OO═C—; wherein T is selected from the group consisting of —CR═CR′R″, an alkyl halide, and —RC═O; wherein R, R′ and R″ are an H, alkyl or aromatic group; wherein a is 0 or an integer; wherein x=1, 2 or 3; wherein y=1, 2 or 3; and wherein x+y=4.
 41. The storage medium of claim 34, wherein the low dielectric constant polymer layer is formed from a polymer material having a dielectric constant of less than 2.6.
 42. The storage medium of claim 41, wherein the low dielectric constant polymer layer is formed from a poly(paraxylylene) having a general formula of —(—C(F_(x)H_(2-x))—(C₆F_(y)H_(4-y))—C(F_(x)H_(2-x))—)—wherein x=0, 1 or 2, and wherein y=0, 1, 2, 3 or
 4. 43. The storage medium of claim 42, wherein the low dielectric constant polymer layer is formed from a poly(paraxylylene)-based material having a general structure of —(CF₂—(C₆H₄)—CF₂)—, and wherein the low dielectric constant polymer layer is deposited with an initial crystallinity of 20-50% in a β₂ phase of the material.
 44. The storage medium of claim 34, wherein the low dielectric constant polymer layer is formed from a monomer having a general formula of X′_(m)—Ar—(CZ′Z″Y′), wherein Ar is an aromatic group or a fluorine-substituted aromatic group, wherein Z′ and Z″ are selected from the group consisting of H, F and C₆H₅, wherein X′ and Y′ are leaving groups removable to generate free radicals, wherein m and n are each equal to zero or an integer, and wherein m+n is less than or equal to a total number of sp² hybridized carbons on Ar available for substitution.
 45. The storage medium of claim 34, wherein the substrate has a surface, and wherein the instructions are executable to direct the wafer processing system to expose the substrate to ultraviolet radiation before depositing the silane material onto the substrate to remove water from the substrate surface.
 46. The storage medium of claim 34, wherein the instructions are executable to direct the wafer processing system to heat the adhesion promoter layer and the low dielectric constant polymer layer under a mixture of 3-10% hydrogen in an inert gas.
 47. The storage medium of claim 34, wherein the instructions are executable to direct the wafer processing system to heat the adhesion promoter layer and the low dielectric constant polymer layer under hydrogen for 0.5-10 minutes.
 48. The storage medium of claim 34, wherein the instructions are executable to direct the wafer processing system to heat the adhesion promoter layer and the low dielectric constant polymer layer under hydrogen for 3-4 minutes.
 49. The storage medium of claim 34, wherein the instructions are executable to direct the wafer processing system to heat the adhesion promoter layer and the low dielectric constant polymer layer under hydrogen to a temperature of 300-400 degrees Celsius. 